I'm using Optimum brand from Staples. They've never given me any problems before.
I have a V4 PS2 with a Magic 3 chip and I have a DVD+R burner and have been using the +R format for a while now.
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Ver.4 is not that good with +R's in General..It's seems like miracle that you even got any +R disc to boot at all..
Starting from Ver.5 and up it shouldn't be a problem but lower than V5 with +R Discs it's questionable..